Mayor Marion Barry, under pressure to reduce the city's record prison population, will declare a second prison emergency today that will allow the city to release 700 to 800 inmates from the District's crammed prisons in a sharply revamped program, sources said yesterday.

The controversial guidelines that dictate which prisoners are eligible for early release have been rewritten to prohibit the release of certain categories of violent offenders, such as robbers and drug dealers, who were released during the first prison emergency, sources said.

Barry's spokesman, John C. White, said yesterday morning that Barry had not acted on the early release proposal but would probably announce a plan today.

The first early release, carried out in July, drew protests. Critics, including Rep. Stan Parris (R-Va.), charged that the program was hastily prepared and sloppily managed. City officials violated a commitment to release only prisoners convicted of "nonviolent crimes," critics contended.

Sources said yesterday that the process had been revised and formalized under a Department of Corrections order setting out new procedures. This time, a point person -- Corrections Department management analyst Theresa Lantz -- will oversee the entire program, sources said.

Under a law that took effect Nov. 14, the mayor has the power to ease prison crowding by declaring a state of emergency and releasing certain inmates up to 90 days early if the prison system's overall population exceeds its official capacity for 30 consecutive days.

On Nov. 27, Corrections Director Hallem H. Williams Jr. and Corporation Counsel Frederick D. Cooke Jr. submitted to Barry a report that cited prison crowding and urged the emergency release.

The city's prisons and halfway houses now hold a record 8,043 inmates, compared with 7,950 at the time of the first emergency release.

The corrections system, which includes the D.C. Jail in Southeast Washington along with nine facilities at Lorton Reformatory in southeastern Fairfax County -- is designed to hold about 7,350 inmates under a regulation that gives each inmate about 60 square feet of living space.

During the first emergency release, from July 3 to Oct. 1, corrections workers complained that they were confused about which prisoners to release, because of discrepancies in a department briefing paper about what constituted a violent crime.

The new law prohibits the mayor from reducing the sentence of any prisoner serving a life term or mandatory sentence or any inmate convicted of a violent felony, including "homicide, rape, assault with intent to rob, a sex offense other than rape, extortion, kidnaping, assault with a dangerous weapon, or armed robbery."

The briefing paper previously given to corrections workers was worded differently.

Parris, whose congressional district includes Lorton, fought vigorously in Congress this fall to overturn the early release program. He said he is encouraged by the tightened regulations of the new emergency plan.

About 815 prisoners were released early during the first emergency. Of those released, 58 were sent back to prison.

Williams has said that the early release program is not a solution to the District's chronic prison crowding, but a stopgap measure. Prisoners are released an average of 19 days early under the emergency program, he said.

Since early releases do not result in permanent reductions in the number of prisoners, the District still faces major long-term problems in its corrections system, officials said.